A cable television network is a known type of communications network that is used to transmit information between a service provider and a plurality of subscriber premises, typically over fiber optic and/or coaxial cables. The service provider may offer, among other things, cable television, broadband Internet and Voice-over-Internet Protocol (“VoIP”) digital telephone service to subscribers within a particular geographic area. The service provider transmits “downstream” signals from the headend facilities of the cable television network to the subscriber premises. “Upstream” signals may also be transmitted from the individual subscriber premises back to the headend facilities. In the United States, the downstream signals are typically transmitted in the 54-1002 MHz frequency band. The upstream signals are typically transmitted in the 5-42 MHz frequency band.
The headend facilities of the cable television network include a large number of RF transmitters that modulate the downstream data onto RF carrier signals for transmission to the subscriber premises. The downstream data may include, for example, broadcast digital television signals, video-on-demand program content, Internet traffic, VoIP telephone signals and the like. The RF transmitters that are used to transmit this downstream data onto the cable television network infrastructure may comprise, for example wideband Quadrature Amplitude Modulation (“QAM”) transmitters that may support one hundred or more QAM channels per RF port. One conventional RF transmitter that may be used in these networks is the Universal Wideband Edge QAM transmitter offered by CommScope, Inc. of Hickory, N.C. The Universal Wideband Edge QAM transmitter has sixteen RF ports and supports 160 QAM channels per RF port for a total of 2,560 channels per transmitter. An international telecommunications standard known as the Data Over Cable Service Interface Specification (“DOCSIS”) specifies standardized parameters for high bandwidth data transfer over cable television networks. Under DOCSIS 3.0, the above referenced channels and the signals transmitted over these channels were referred to as QAM signals and QAM channels. Under DOCSIS 3.1, the QAM channel is now referred to as an SC-QAM channel, where “SC” stands for “single carrier.” DOCSIS 3.1 also supports an orthogonal frequency division multiplexing (“OFDM”) channel that is based on multiple QAM channels, and this OFDM channel is sometimes referred to as a “Multi-Carrier QAM channel,” which is why the normal QAN channels are now referred to as SC-QAM channels.
Subscribers of cable television, Internet and VoIP services may be very demanding, and may find even occasional service outages to be unacceptable. Many business subscribers rely heavily on their Internet and VoIP service to conduct their daily operations, and hence even short service outages can have significant impact on such subscribers. Accordingly, service providers are under increased pressure to reduce the incidences of service outages and to reduce the length of any service outages that occur.